文章目錄

原题链接 http://projecteuler.net/problem=53

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Combinatoric selections

There are exactly ten ways of selecting three from five, 12345:

123, 124, 125, 134, 135, 145, 234, 235, 245, and 345

In combinatorics, we use the notation, C(5,3) = 10.

In general,

C(n,r)=n!/(r!(n-r)!), where r <= n, n! = n (n - 1) 3 2 * 1,and 0! = 1.

It is not until n = 23, that a value exceeds one-million: C(23,10) = 1144066.

How many, not necessarily distinct, values of C(n,r), for 1 <= n <= 100, are greater than one-million?

组合选择

从五个,12345中选出三个一共有10中方法

123, 124, 125, 134, 135, 145, 234, 235, 245, and 345

在组合中我们使用记号C(5,3) = 10.

一般来说

C(n,r)=n!/(r!(n-r)!),r <= n, n! = n (n - 1) 3 2 * 1, 且0! = 1

直到n = 23,才出现值超过1000000: C(23,10) = 1144066.

求一共有多少个值,没有必要是唯一的,使得C(n,r), 1 <=n<= 100,超过1000000?

解答:

遍历吧。

文章目錄